Method of making coils



Oct. 4,1927. 1,643,998

B. R. SCOTT METHOD OF MAKING COILS Original Filed Feb. 19, 1926 Fig. 2-

INVENTOR .Beverlc zy Rand 1 12 Scott,

" ATTORNEY I Patented Oct. 4,1927.

UNITED STATES BEVERLEY RANDOLPH SCOTT, OF WOODLYNNE, NEW JERSEY, ASSIGNOR TO THE PATENT OFFICE} HARLUND MANUFACTURING COMPANY, INCORPORATED, ACORPORATION OF NEW YORK.

mn'rn'on or MAKING coins.

Original application filed February 19, 1926, Serial No. 89,292.Dividedand this application filed July 29,

1927. Serial No. 209,276. 1

My invention relates particularly to wire coils used for variouspurposes such as elec-' tric inductances. I

One object is to providea coil of high inductance value and lowdielectric loss, a relatively low resistance and small distributedcapacity.

Another object is to provide a coil which can be readily handled andmounted.

Another object is to provide a coil having permanent and uniformcharacteristics. I I have solved the problem by the simple ex edient ofwinding a coil upon a very thm layer of dielectric material such ascelluloid to which it is permanently anchored by surface adhesion. Themethod of manufacture which'will be hereinafter described is inexpensiveand makes it possible to permanently maintain any desired spacing of '20the various turns.

Fig. 1 is a side View of a coil made according to my invention.

Fig. 2 is an end view of the same.

Fig. 3 is a perspective view of a mandrel showing one method of applyingthe dielec-- tric.

Figs. 4 and 5 are' diagrammatic end views of two other arrangements ofthe support coil of angular cross-section supported on w two stri s ofdielectric.

Fi is an enlarged longitudinal see.-

tiona liview showing a fragment of a coil in 3 process ofmanufacture.

Fig. 8 is a similar sectional view showing the same after the wire hasbeen permanently secured-in place.

Th foundation 10 of the coil is made up of=.ione-or more strips of anon-conducting andexpending the mandrel.

simple expe vent, ,such as'ethyl-acetate, to the material l along the lne of overlap, the edges of the the coil I preferably employ a Accordingto the prefer-red methodof of celluloid, say five-thousandths of an inchthick, is wrapped around the mandrel and the edges of the sheetoverlapped, as indicated in Fig. 3, and stuck togethei' by the ient ofapplying a suitable solmanufacture, a very thin foundation sheet sheetbeing drawn together smoothly and pressed together immediately after thesolvent is applied. 1 have found that this operation of cementing theedges together can be greatly facilitated by the use of a sphincterspring 15. This "spring'normally restsin a groove 16 in one end of themandrel and is run along the surface of the celluloid as soon as theoverlapping edges have been moistened with the solvent. Springs 16' holdthe mandrel parts yieldingly together.

. Whenthe edges of the sheet have been united on the mandrel the mandrelis expanded in the usual manner by sim ly drivmg the shaftlongitudinally. This places the celluloid tube under tension and holdsit smooth. V -The mandrel is then placed in a Winding machine and thewire wound on it under tension. This tension should remain substantially constant throughout the windin operation and the feeding ofthe wire .shoul of course be at the proper rate to laythe wire with thedesired spacing between adjacent turns;

' When the coil has been wound, a suitable solvent, such asethyl-acetate is appliedto the foundation between the adjacent turns ofthe wire, for instance, by means of a brush. Thissolvent also penetratesthe insulation \of the wire and immediately softens the surface of thefoundation adjacent the wire.

The coil being under tension, as before described, of course tends tocontractin diameter and its inner surface thus sinks slightly in to thesoftened surface of the celluloid or theflike. "The change in conditionbefore and after the application of the solvent is shownby thedifference between therelative The shaft mey be retracted andfthemandrel contracted and withdrawn as soon as the material .hassubstantially which requires only a few minutes. The finished coil will,however, continue to dry out for some time, the length of time varyingwith the composition of the material, the nature of the solvent and theamount aplied, as well as the atmospheric conditions. n drying out thecoil shrinks lengthwise,

sometimes as much as 10%. I

\ The coil may be wound at any length desired for special purposes. Themethod of manufacture lends itself particularly to the production oflong tubes which/can be very readily cut up into such lengths as may bedesired which is much cheaper than 'the winding of small individualcoils.

In the manufacture of vthese tubes, particularly in small diameters,there is sometimes a tendency for the tube to warp when made as abovedescribed, due to the overlap ed joint along one edge. This can be reaily avoided, however, by using two strips, such as 20 and 21, as shownin Fig. 4, so that there will be oppositely disposed joints which willoffset each other in the shrinking rocess.

It shoul shown for instance in Fig. HereI have shown four strips 23 withspaces 24 between them, which form an open work or skeleton tube. A coilwound in this manner has an added advantage of reducing the dielectricmaterial to a minimum. Such a coil having no overlapped joint has notendency to warp in drying.

Although the coil is preferably circular in cross-section, it should beunderstood that certain features of the invention are applicable tocoils of other.cross-sections, for instance, in Fig. 6, I have shown asquare coil wound on two se arate strips 25 on o posite sides. Thiswould, of course, leave t e portions 26 of the wires on the intermediatesides of the coil spaced apart from each other without sup orts exceptat the edges of the strips 25. This requires much less of the foundationmaterial.

Coils wound according to my invention may be used for various purposes,such, for instance, as radio frequency variable couplers, antennacouplers, inters'tage couplers, neutrodyne coils, short wave coils, etc.As they are very light in weight and self supporting they can be easilyhandled and mounted in various ways This is a division from myapplication #89,292 filed Feb.'19,, 1926, in-which I broadlv claim acoil comprising a helix of conducting wire together with a sheet ofinsulating material touching and adhering to a surface of the helixthroughout substantially the entire extent of the helix, the wirehardened,

also be .understood that a number of foundation strips may be usedandthat these strips may be spaced apart as ,making contact with thesheet 'on only a terial on a mandrel, winding insulated wire tightlythereon, then applying a solvent to I the outer surface of the materialbetween the turns of wire, thereby causing the wire to become partiallyembedded in the material and then allowing'the material to dry.

2. The method of making a coil which comprises winding wire. undertension onto thin celluloid, then applying solvent to the surface ofthecelluloid to soften it and-allow the wire to become partiallyembeddedand then allowing the celluloid to dry and the coil to shrinklengthwise. Q

v3. The method of forming a wire coil which comprises forming a tubeofmaterial such as celluloid, applying pressure to the inside of thetube, winding turns of wire tightly on the tube, applying a solvent tothe surface of the tube between the turns of wire and then removing thepressure from the tube and allowing thetube to dry.

4. The method of supporting wire which consists in placing insulatedwire ona f0un-' dation of celluloid in spacedfapa'rt relation,

applying solvent to the celluloid between the adjacent walls of the wireso as to cause the celluloid to impregnate the insulation and allowingthe. celluloid to set and adhere to the insulation.

5. The method of making a helical induc-,

tance coil comprising placingon a'mandrel a band of insulating materialhaving an insulating binding coating on the outer surface thereof,assembling the turns of said coil on said binding surface, hardeningsaid binding surface after said winding is in place and then removingsaid mandrel after said binder has hardened.

6. The method of supporting wire which comprises layin the wirein spacedrelation on a celluloid-1i e foundation, softening the foundation with asolvent such as ethyl acetate between adjacent portions of the wire,allowing the wire to become sli htly embedded in the foundation andthena low-- ing the solvent to evaporate and the foundation to hardenandadhere to the wire.

7.'The method of formin a coil which comprises, first forming a tu e ofcelluloid-' like material by joining the edges of a sheet of suchmaterial, moistenin one edge with a solvent and causin 'the e ges toadhere to each other, then tig tly winding wire on the tube, theadjacent turns of wire being spaced apart from each other, then applyina volatile solvent to the material between 0 turns so as to soften thematerial and permit the wire to be slightly embedded in the softenedsurface of the material and then allowing the solvent to evaporate untilthe material sets and holds the turns in place.

8. The method of securing together the turns of wire of acoil whichconsists in roviding a support having an insulating b1nding substance atthe outer surface thereof which is hard at ordinary room temperature,arranging a coil on the support, softening the surface of the substanceso as to allow the coil to sink slightly into the surface at the pointsof contact between the coil and the surface, then hardening the bindingsubstance. V 4 I 9. The method of assembling an inductance coil on asupport which consists in providing a support aving a surface ofcelluloid, applying to the celluloid surface insusoft enough adjacentthe coilto allow the Wire of the coil to sink into the softened part,and subsequently allowing the solvent to evaporate and the celluloidsupport to set and adhere to a relatively small arc of th wire.

10. The method of forming a coil which comprises forming a tube ofmaterial whose surface is capable of being softened, supporting saidtube on the interior, stretching the material to hold it smooth, windinga conductor on said tube under tension. softening the surface of thetube immediately adjacent the conductor and allowing the material toharden.

BEVERLEY RANDOLPH scorn.

